Filament winding

ABSTRACT

THIS INVENTION RELATES TO FILAMENT WINDING AND PARTICULARLY TO WINDING PRE-IMPREGNATED TAPE-LIKE FILAMENTARY MATERIAL ON NON-CYLINDRICAL SURFACES, AND COMPRISES A CUTTER FOR SPLITTING THE TAPE ENDWISE INTO A PLURALITY OF FILAMENTARY ELEMENTS AND MEANS FOR EFFECTING A TAKE-UP ACTION INDIVIDUALLY UPON EACH ELEMENT, THEREBY REDUCING THE SHINGLING EFFECT INHERENT IN WINDING A TAPE ON A CURVED SURFACE.

. 26, 1972 GOLLADAY ET AL 3,797,415

FILAMENT WINDING OriginalFiled Sept. 20, 1968 FIG. 3

United States Patent 3,707,415 FILAMENT WINDING Arthur D. Golladay and Kevin E. Moran, Cumberland, Md., assignors to Hercules Incorporated, Wilmington, Del.

Original application Sept. 20, 1968, Ser. No. 761,277, now Patent No. 3,565,726, dated Feb. 23, 1971. Divided and this application Oct. 9, 1970, Ser. No. 79,697

Int. Cl. B65h 81/08 US. Cl. 156-169 3 Claims ABSTRACT OF THE DISCLOSURE This invention relates to filament winding and particularly to winding pre-impregnated tape-like filamentary material on non-cylindrical surfaces, and comprises a cutter for splitting the tape endwise into a plurality of filamentary elements and means for effecting a take-up action individually upon each element, thereby reducing the shingling effect inherent in winding a tape on a curved surface.

This application is a divisional of application Ser. No. 761,277, filed Sept. 20, 1968, now US. Pat. No. 3,565,- 726.

The present invention relates to a method for making filament wound articles from tape-like filamentary materials and particularly for making filament wound articles having non-cylindrical or curved surfaces.

In order for a filament winding operation to proceed at a speed that is commercially economical, the filaments are laid on the winding surface as tapes rather than as individual filaments so that in a single turn of the winding surface the number of filaments laid on the winding surface is equal to the number of filaments in the width of the tape. However, in using a tape-like filamentary material to wind a non-cylindrical article such as an article having a conical surface, there are variations in the diameter of the windnig surface across the width of the tape. Thus, the length of the path on the winding surface followed by the different transverse increments of the tape vary between a path of maximum length at one edge of the tape and a path of minimum length at the other edge of the tape. For example, in winding a conical surface with the tape running spirally from the large end of the cone to the small end, the path on the winding surface that is followed by the edge of the tape that is toward the small end of the winding surface is shorter than the path followed by the opposite edge of the tap. There is thus an excess length in the filaments at the edge following the minimum length path. Because of this excess length, this edge is loose and stands out from the winding surface in what may be termed a shingling effect. This looseness causes voids in the wound structure and reduces the strength of it.

In filament winding operations, handling and accurately laying a relatively wide tape-like arrangement of individual filaments is facilitated by preforming the filaments into a coherent tape that is bound together by the binding material used for binding the filaments in the wound structure, which binding material is pre-impregnated and partially cured. In contrast to a preimpregnated tape, in a windingoperation in which the filaments are assembled into a band and impregnated with the resinous binding material as it is being wound, the filaments are loose and it is diflicult to control them accurately enough as they are laid on the winding surface in order to avoid overlapping of the filaments and gaps between adjacent filaments, or other void-producing winding errors. When the filaments are pre-formed into tapes consisting of a plurality of fila- 3,707,415 Patented Dec. 26, 1972 ments, for example in a single layer of filaments in a sideby-side relation, winding errors are reduced since it is necessary only to lay the adjacent tapes in edge-to-edge relation on the winding surface.

The objects of this invention are to provide a method for making filament-wound structures of non-cylindrical configuration, which method and apparatus is capable of relatively high production rates and will inexpensively produce high quality wound structures with a minimum of voids and winding errors. Further objects of this invention will be evident from an understanding of the invention as hereinafter described.

Briefly, the above objects have been achieved by using filaments in the form of a pre-impregnated tape in which the individual filaments are bound together by the partially cured binding material. The tape may be of sufficient width to provide for an economical winding operation but, prior to winding, is divided into a plurality of narrow winding strips. The shingling effect produced by the difference in the diameter of the winding surface over the width of the tape is thus reduced. The accumulated difference in the lengths of the winding paths of the different winding strips is withdrawn from the system by take-up devices and stored until the end of the winding cycle, at which time it is cut off to restore the tape to a starting condition before initiating the next cycle.

With the above and other objects in view, the present invention is hereinafter described with reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary elevational view of a winding apparatus embodying the present invention.

FIG. 2 is a fragmentary sectional view taken substantially on the line 22 of FIG. 1.

FIG. 3 is a fragmentary detail view showing the tape guide of the apparatus of FIG. 1.

FIG. 4 is a diagrammatic view illustrating the tapelaying operation of this invention.

With reference to the drawings, there is illustrated a winding machine 1 having a rotating winding shaft 2 that is driven by a drive shaft 3 having a gear 4 that meshes with a gear 5 on the shaft 3. Mounted on the shaft 3 and rotatable therewith is a mandrel 6. As ilustrated, the mandrel 6 is substantially frustroconical in shape with the winding surface 7 thereof decreasing in diameter from the large diameter end 8 to the small diameter end 9.

The filamentary winding material that is to be wound on the winding surface 7 of the mandrel 6 is supplied in the form of a tape 13 from a spool 10 that is mounted on a spool pin 11 upstanding from a platform 12 of a tape feed mechanism. The spool 10 is loose on the pin 11 so that it is free to turn as the tape 13 is pulled from it. The platform 12 is mounted for sliding endwise or axially of a pair of rods 14 that are disposed parallel to the axis of the winding shaft 2, and which define the tape-laying axis along which the tape feed mechanism is moved. The platform 12 is adapted to be driven along the rods 14 by a drive link 15 that may be actuated by a programmed mechanism (not shown) whereby the platform will traverse the mandrel 6 and the tape 13 is laid onto the winding surface 7 in accordance with a pre-determined pattern.

From the spool 10, the tape 13 passes through a tension device 16 that consists of a guide pin 17 and a frictioning drum 18, both of which are supported on a supporting plate 19 upstanding from the platform 12. In order to adjust the drag on tension imposed upon the tape 13, the pin 17 may be adjustable (not shown) to increase or decrease the angle of engagement between the tape 13 and the drum 18, or alternatively, the drum 18 may be provided with a rotatable shaft (not shown) having an adjustable brake mechanism for imposing a drag thereon. In either case, the surface of the drum 18 may be provided with a frictioning material.

The tape 13 passes from the drum 18 over a cutter 20 which may be in the form of a rotary blade that is journaled on the supporting plate 19. The cutter 20 splits the tape 13 longitudinally substantially along its centerline, into the winding strips 21a and 21b, each having a width substantially equal to one-half the width of the tape 13. From the cutter 20, the strips 21a and 21b pass individually over one of a pair of guide pins 22 and 23, over a guide roller 24 of individual take-up devices 25, through a guide 2'6 carried by the platform 12 and onto the winding surface 7 of the mandrel 6.

There is a separate take-up device 25 for each of the strips 21a and 21b, each of which take-up devices comprises a bar 27 pivoted intermediate its end on a pivot 28 carried by a support 29 upstanding from the platform 12. The guide roller 24 is mounted for turning freely upon one end of the bar 27 while the other end of the bar 27 carries a weight 30 that is adjustable lengthwise of the bar and adapted to be secured in adjusted position. The weight 30 imposes a pivotal bias on the bar 27 in the direction whereby the roller 24 effects a take-up action on the length of the respective strip 21a or 21b that is between the mandrel 6 and the drum 18, thus removing and temporarily storing any excess length of the strips that may be present.

In operation, rotation of the mandrel 6 pulls the strips 21a and 21b taut against the drum 18 of the tension device 16, which initially lowers the take-up bars 27 into their stop positions as determined by a stop 31 on the bracket 29, and then pulls the tape 13 from the spool 10 and through the tension device 16. As the tape 13 advances from the tension device 16, it passes over the cutter 20, which splits it longitudinally into the two winding strips 21a and 21b, each of which then passes individually over the roller 24 of the respective take-up device 25 and onto the mandrel 6.

With reference to FIG. 4, if the tape 13 were laid as an unsplit tape 13a onto the winding surface 7, there would be what is herein referred to as a tight edge 32, which is the edge at the largest diameter of the winding surface 7 over the width of the tape 13 and therefore the edge that follows the maximum length path on the winding surface 7. The edge 32 is drawn against the surface 7 by a force determined by the tension device 16. The opposite edge of the tape 13a constitutes a loose edge 33 which, because the diameter of the winding surface 7 at this point is reduced relative to the diameter at the edge 32, and because the length of the tape 13a drawn from the spool 10 is determined by the engagement of the tight edge 32 with the surface 7, stands out from the surface 7 by a distance determined by the slope of the surface 7 over the width of the tape 13a. Because of the reduced diameterof the winding surface 7 under the edge 33, the projection of this edge into the winding surface 7 as the latter rotates defines a path on the winding surface that is shorter than the path defined by the edge 32 so that there is an excess length at the edge 33. By splitting the tape 13a along its centerline into the two winding strips 21a and 21b, and by effecting a take-up action individually on the strips, there is removed from the system the accumulated excess length at the centerline of the tape, which is now the loose edge 33b of the strip 21b, as the leading edge 32a of the strip 21a is drawn against the winding surface to form a new tight edge.

Accordingly, as the winding operation proceeds, the take-up device 25 associated with the strip 21a moves away from the stop 31 as it accumulates the excess length of that strip. At the end of a tape-laying cycle, which may be one or more passes across the winding surface, the accumulated excess is removed and discardedas waste. During the accumulation of the excess, the tape 13 is pulled from the spool 10 by the mandrel '6 through the strip 21b, the bar 27 associated with this strip being maintained against the stop 31.

The guide 26 is designed to separate the two filamentary strips 21a and 21b and to keep them separated until immediately before they are laid on the winding surface 7, thus minimizing the possibility that they may inadvertently come into contact and become adhesively secured together. Therefore, the guide 26 comprises an eye 35 that is mounted on the platform 12 for rotation relative thereto and having a shank portion extending down through an aperture 36 in the platform 12, the eye having a guide opening 37 centrally thereof. Beneath the platform 12, there is secured to the eye 35 a support plate 38 on which are journaled a pair of spaced guide rolls 39 and 40 and a delivery roll 41 at which the two strips 21a and 21b are rejoined in edge-to-edge relation. With the eye 35 mounted for turning freely in the platform 12, that is, about its vertical axis in FIG. 3, the delivery roll 41 is free to align itself with the delivery angle of the tape.

While the tape 13 is the illustrated embodiment of the invention is divided into two strips 21a and 21b, it will be obvious that it may be divided into several strips, thus further reducing the width of the individual winding strips and the spacing of the loose edges of them from the winding surface. By way of example, a tape 13 that isinitially one eighth of an inch in width may be split into four winding strips, each of which is one thirty-second of an inch in width. The excess length accumulated at the loose edge in winding a conical surface, which excess is pro hibitive with a tape that is one-eighth inch wide, is reduced to acceptable limits with winding strips that are one thirty-second inch wide. At the same time, the advantages associated with feeding a plurality of filaments simultaneously in a tape onto a winding surface, that is, the increased winding speeds and reduced winding errors, are not materially sacrificed. While the filaments are preferably bound into a coherent tape as in the usual prc-impregnated tapes used in filament windings, the present invention is also useful with noncoherent tapes.

The cutter 20 is preferably a rotary cutting blade but may also be a flat blade such as a razor blade or may be a wire. Inasmuch as the tape 13 consists essentially of filaments extending in an oriented or parallel relation lengthwise of the tape and interconnected laterally only by the partially cured binding material, which is relatively weak, the tape can be split lengthwise relatively easily. Thus, a cutter 20 in the form of simple wires can also be used.

The winding tension on the strip 21b is determined essentially by the force required to pull the tape 13 through the tension device 16, while the take-up device 25 associated with the strip 21b becomes in effect a fixed guide since it is held in a stop position with the bar 27 against the stop 31. The strip 21a is loose except for the tension imposed upon it by the respective take-up device 25, and this tension is preferably made as close as possible to that on the strip 21b. Since the tension on the strip 21a also tends to pull the tape 13 through the tension device 16, it is preferably adjusted to substantially one-half the force required to pull the tape through the tension device 16 so that the tensions on the strips 21a and 21b are substantially balanced. The tension on the strip 21a is adjusted by adjustment of the weight 30 lengthwise of the bar 27. It will be obvious that the bias of the bar 27 may be achieved by means other than the weight 30, for example, by an air cylinder or spring. A further alternative would be a positive feed of the capstan type which feeds the band of tape into the system in response to an increment of tension over and above the normal winding tension.

What we claim and desire to protect by Letters Patent 1. A method of making a filament wound structure from a tape of filamentary material wound upon a rotating winding surface on which the winding path of the tape on the winding surface varies in length over the width of the tape from a maximum winding path at one edge of the tape to a minimum winding path at the other edge of the tape, comprising, advancing the tape toward the winding surface, dividing the tape into a plurality of longitudinal narrow strips, winding said strips in accordance with a winding pattern onto the winding surface, simultaneously taking up under tension and accumulating the excess length from each of the strips that has a winding path shorter than the maximum winding path, and periodically removing the accumulated excess length of strips.

2. A method in accordance with claim 1 in which the filamentary tape is pre-impregnated with a binding material that is partially cured to bind and thereby render the same coherent.

3. A method in accordance with claim 1 in which 15 substantially constant tension is applied to each of the narrow strips.

References Cited UNITED STATES PATENTS 2,594,693 4/1952 Smith 156-175 X 3,506,420 4/1970 Jackson, Jr., et al. 156-167 X 3,290,197 12/1966 Carmody 156175 X 10 DANIEL J. FRITSCH, Primary Examiner US. Cl. X.R. 

